This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 18 |
| 6 | 116 |
| 7 | 1060 |
| 8 | 13019 |
| 9 | 193425 |
| 10 | 3313522 |
| 11 | 63667788 |
| 12 | 1351700744 |
| 13 | 31390695708 |
| 14 | 791372281393 |
| 15 | 21523271532811 |
| 16 | 628166776833181 |
| 17 | 19582955637428422 |
| 18 | 649472761243051940 |
| 19 | 22833268501579122332 |
| 20 | 848230375982060558217 |